[systemd-devel] Systemd and cgroup management (and libcgroup)

[Balbir Singh]

On Tue, Nov 1, 2011 at 3:02 AM, Lennart Poettering
<lennart at poettering.net> wrote:
> On Mon, 31.10.11 14:43, Jan Safranek (jsafrane at redhat.com) wrote:
>
>> >> Even if there is, then it looks like systemd is better place to manage
>> >> it as it already is setting up the whole system and top level hierarchies.
>> >> Thanks to Jason for the suggestion.
>>
>> Systemd pretty much covers most of the use cases. The main reason to
>> keep separate cgconfig is mounting several controllers together in one
>> hierarchy - AFAIK systemd won't support this mounting. Still, systemd
>> will happily put services to cgroups there.
>
> We actually do support mounting hierarchies jointly these days. Use
> "JoinControllers=" to achieve that. By default we moint and cpu and
> cpuacct together.
>

cool! Is it possible to UnJoinControllers at runtime and ask for a
different binding without a reboot?

>> Lennart wrote once on previous discussion [1]:
>>
>> <cite>
>> systemd will create automatic groups for users and services, but will
>> not help you to set up any more complex hierarchy then just 1:1 service
>> to cgroup mappings.
>>
>> As soon as you want a more complex tree, with multiple levels or
>> something like this you will need something like cgconfig which allows
>> you to create any tree you want.
>> </cite>
>>
>> Question is, if we really need complex cgroup hierarchies and/or
>> multiple controllers in a hierarchy.
>
> I am quite sure that sooner or later some folks will need complex cgroup
> hierarchies, for example if they want to give a group "teachers" a more
> resources than the group "students" or so. I am very sure that some
> people want features like that, but I am also quite sure I don't want to
> cover that in systemd, which is why I am happy if cgconfig could fill in
> that void. I think systemd will cover 90% of the use cases, but the 10%
> that are left are valid too, and cgconfig sounds like a useful tool to
> make that work.

Yes, I agree. I wonder if using two tools hurts user experience, but
using two configurations is quite specialized and if we have it well
documented, we should be good

Balbir Singh